This application is generally related to the subject matter of commonly assigned U.S. Pat. Nos. 4,746,270 and 4,925,367, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates in general to coolant pumping systems used with internal combustion engines in automotive vehicles, and in particular to electrically-driven impeller-type coolant pumping systems for use with internal combustion engines in automotive applications.
2. Description of Related Art
In conventional water pump systems used on automobiles, a drive belt and pulley are used to provide the drive rotation to the coolant pump shaft. The coolant may be of any suitable type, such as the commonly used mixture of water and anti-freeze. A gear or chain drive is sometimes used instead of a belt and pulley. A double set of bearings are typically provided in the pump casing to resist the large external side load forces generated by such a pulley, gear or chain drive. As is well known, when these side load forces are considered, the overall forces experienced by the pump shaft are inherently unbalanced. On account of the unbalanced force vector to the pump shaft, it is necessary to suitably strengthen the pump assembly, pump shaft and its ball bearings to handle expected loads and overloads. This adds to the cost and weight of the coolant pump.
The use of the aforementioned side-loaded drive systems also create an additional expense in that the crankshaft or camshaft of the vehicle must be extended through the engine block wall so that the master drive pulley or gear can be mounted on the shaft. The master drive pulley and belt or gears also add expense and weight to the vehicle's power plant. Passing the crankshaft or camshaft through the engine block wall also requires that appropriate measures be taken to seal the shaft bearing from environmental contamination such as moisture, dirt and dust, or acidic or salty water sprayed up from road surfaces. A common failure mode for water pumps is the failure or wear of the water pump bearing. Severe bearing wear often results in damage to the flexible coolant face seal assembly, which allows coolant to escape from the engine's cooling system, thus presenting further problems. If the pump bearings did not fail in the first place, many such failures of the flexible face seal assembly could be avoided, along with the resultant loss of engine coolant, and destruction of the pump shaft on account of scoring and galling.
Accordingly, it would be very beneficial to provide a direct-drive water pump system which solves most if not all of the foregoing problems, By "direct-drive" we mean a drive system that avoids applying external side loads to the pump shaft and bearing set which supports the pump shaft. It would also be useful to eliminate the need to extend the crankshaft or camshaft outside of the engine block to provide the rotational power required to drive the coolant pump. It would also be desirable to provide a new design for a coolant pump system which can be easily adapted to handle different pumping requirements. Finally, it would be useful to drive both the coolant pump and radiator cooling fan with the same direct-drive system.
In light of the foregoing problems with conventional pulley-driven coolant pumping systems, it is a primary object of the present invention to provide a coolant pump arrangement for an internal combustion engine which is powered by an electric motor.
It is another object of the present invention to provide an electric-drive motor which is mounted directly to the coolant pump body, to eliminate the bearing assembly of the coolant pump.
It is a further object of the present invention to provide a coupling mechanism which allows the pump to be quickly coupled and uncoupled from the electric motor that drives it.
It is yet another object to provide a bearingless coolant pump with an in-line direct drive system which eliminates external side loads on the pump shaft.
Still another object of the present invention is to provide a coolant pump system driven by an electric motor with a double-ended shaft so that the cooling fan can also be driven by the electric motor.